1. Field of the Invention
The present invention relates to semiconductor crystal growth, and more particularly, to growth of dendritic web ribbon semiconductor crystals from a semiconductor melt.
2. Description of the Prior Art
In the past, a well known method of forming dendritic semiconductor web ribbons has been to immerse a crystal seed having the desired crystallographic orientation into a semiconductor melt. A crystal web button then forms about the seed at the surface of the melt. Once the seed button reaches a desired width, the seed is slowly withdrawn from the melt, causing the web button to grow in length.
One disadvantage of the conventional process described above has been the practical limitations placed upon the width to which the button may be allowed to grow prior to initiating the upward pull to start ribbon growth. The primary constraint on this width, and therefore the initial area rate of crystal growth, has been the large asymmetrical forces which develop on the seed button about the seed during initial button seed withdrawal. Since the seed is near its melting point, the large asymmetrical forces tend to bend it, causing the web button to tip. If the web button tips a sufficient amount, web growth will be lost due to disruption of crystallographic orientation of the ribbon, and rupture of the liquid semiconductor meniscus.